Controllable synthesis of MoS₂/graphene low-dimensional nanocomposites and their electrical properties

Long, Le Ngoc,Thi, Pham Tan,Trung Kien, Pham,Trung, Pham Thanh,Ohtani, Masataka,Kumabe, Yoshitaka,Tanaka, Hirofumi,Ueda, Shigenori,Lee, Hyoyoung,Thang, Phan Bach,Khai, Tran Van Elsevier 2020 APPLIED SURFACE SCIENCE - Vol.504 No.-

<P><B>Abstract</B></P> <P>In this study, a novel hydrothermal route has been developed for the synthesis of MoS<SUB>2</SUB>/graphene composite with controllable structures, in which ammonium molybdatetetrahydrate, as-prepared graphene oxide (GO), and thioacetamide were used as staring materials. Effects of Mo<SUP>4+</SUP>-to-C precursor ratios and crystalline time on the structures, components and morphologies of MoS<SUB>2</SUB>/graphene were investigated. MoS<SUB>2</SUB>/graphene samples were characterized using XRD, FESEM, HRTEM, FTIR, Raman spectroscopy, HAADF-STEM/EDS, HXPES and electrical measurements. The results show that petal-like MoS<SUB>2</SUB> nanostructures with ultrathin petals (~1–10 layers) and coexistence of 1T- and 2H-MoS<SUB>2</SUB> phases can be synthesized on graphene surface in a short time (~2 h). Comparison of crystallization conditions, we found that the crystallization time had a significant effect on the size of the MoS<SUB>2</SUB> nanopetals. The shorter the reaction time is, the thinner the petal-like MoS<SUB>2</SUB> nanoscale is. On the other hand, by adjusting the ratios of Mo<SUP>4+</SUP>to C (denoted as: MoS<SUB>2</SUB>/C (1:2), MoS<SUB>2</SUB>/C (3:2), MoS<SUB>2</SUB>/C (2.5:1) and MoS<SUB>2</SUB>/C (3:1)), different MoS<SUB>2</SUB>/graphene architectures including “sandwich-liked”, “layer–by–layer” and “anchored” can be obtained. On the basis of these results, a possible growth mechanism of MoS<SUB>2</SUB>nanopetals on GO was proposed. Interestingly, the as-synthesized material depicts its memristive behavior through the Volt-Ampere characteristics, suggesting a potential application in logic memory devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel hydrothermal route has been developed for the synthesis of MoS<SUB>2</SUB>/graphene composite with controllable structures. </LI> <LI> The effects of Mo<SUP>4+</SUP>-to-C precursor ratios and crystalline time on properties of MoS<SUB>2</SUB>/graphene were investigated by FESEM, HRTEM, XRD, FTIR, Raman spectroscopy, HAADF-STEM/EDS and HXPES. </LI> <LI> The memristive properties of the MoS<SUB>2</SUB>/graphenenanocomposite were presented. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fabrication of graphene‑assisted voltammetry platform for the detection of nitrate ions in PM2.5

Huadong Li,Yang Zhang,Kaiwen Feng,Chuan Wei 한국탄소학회 2023 Carbon Letters Vol.33 No.7

This study presents the fabrication and application of a graphene-assisted voltammetry platform for the sensitive detection of nitrate ions in PM2.5 (atmospheric aerosols with a maximum diameter of 2.5 μm). The MoS2/ reduced graphene oxide/ glassy carbon electrode ( MoS2/rGO/GCE) was prepared using a simple and efficient electrochemical deposition method. The rationale behind selecting MoS2/ rGO stems from their individual properties that, when combined, can enhance the electrode’s performance. MoS2 offers excellent electro-catalytic activity and selectivity for nitrate ion detection, while rGO provides high conductivity and a large surface area for enhanced sensitivity. The electrochemical performance of MoS2/ rGO/GCE was investigated and compared with MoS2/ GCE and bare GCE using cyclic voltammetry and electrochemical impedance spectroscopy. The results demonstrated that MoS2/ rGO/GCE exhibited enhanced electro-catalytic activity, high conductivity, and improved selectivity for nitrate ion detection. The optimal pH value for detecting nitrate ions was determined to be 8.0. Differential pulse voltammetry (DPV) was employed to investigate the linear range and detection limit of nitrate ions on MoS2/ rGO/GCE, resulting in a linear range from 1 to 300 μM and a detection limit of 0.35 μM. The reproducibility and the stability of MoS2/ rGO/GCE were assessed, showing satisfactory performance. Real sample analysis from Chengdu City showed a strong correlation between the results obtained using MoS2/ rGO/GCE and ion chromatography, highlighting its potential application in monitoring nitrate ions in PM2.5. The findings of this study contribute to the development of a graphene-assisted voltammetry platform for sensitive nitrate ion detection in PM2.5, offering potential benefits for real-time air pollution monitoring and environmental health assessments.

Facile and cost-effective growth of MoS₂ on 3D porous graphene-coated Ni foam for robust and stable hydrogen evolution reaction

Hussain, Sajjad,Vikraman, Dhanasekaran,Truong, Linh,Akbar, Kamran,Rabani, Iqra,Kim, Hyun-Seok,Chun, Seung-Hyun,Jung, Jongwan Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.788 No.-

<P><B>Abstract</B></P> <P>To replace the costly, noble platinum electrocatalyst, the inexpensive, earth abundant and highly efficient electrocatalysts of layered transition metal dichalcogenides (TMDs) are explored for the hydrogen evolution reaction (HER). This paper describes cost-effective synthesis of 1T-MoS<SUB>2</SUB> on 3D-graphene/Ni foam (NF) via a facile solution bath approach as an electrocatalyst for HER. The improved HER performances were observed due to the 3D-structure of MoS<SUB>2</SUB>/graphene. HER performance of MoS<SUB>2</SUB>/graphene/NF electrocatalyst exposed a superior catalytic performance with the low overpotential (−89 mV vs RHE) to drive the 10 mA cm<SUP>−2</SUP>, steep Tafel slope (45 mV dec<SUP>−1</SUP>), large exchange current density (4.16 × 10<SUP>−1</SUP> mA cm<SUP>−2</SUP>), and robust stability over 18 h. Density functional theory (DFT) calculations also confirmed the reduced Gibbs free energy for H-adsorption (ΔG<SUB>H</SUB>) for MoS<SUB>2</SUB>/graphene compared to MoS<SUB>2</SUB>. The observed results suggest that the 1T-MoS<SUB>2</SUB>/graphene/NF is an interesting alternative to platinum-based catalyst for boosting HER efficiency.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Active electrocatalyst of MoS<SUB>2</SUB> decorated on graphene/NF by chemical route. </LI> <LI> Raman and XRD results confirmed the observation of 1T-MoS<SUB>2</SUB>. </LI> <LI> The robust stability over 18 h with over potential of 89 mV vs RHE was observed. </LI> <LI> DFT calculations explained in terms of density of states for high HER performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Low-temperature wafer-scale growth of MoS₂-graphene heterostructures

Kim, Hyeong-U,Kim, Mansu,Jin, Yinhua,Hyeon, Yuhwan,Kim, Ki Seok,An, Byeong-Seon,Yang, Cheol-Woong,Kanade, Vinit,Moon, Ji-Yun,Yeom, Geun Yong,Whang, Dongmok,Lee, Jae-Hyun,Kim, Taesung Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.470 No.-

<P><B>Abstract</B></P> <P>In this study, we successfully demonstrate the fabrication of a MoS<SUB>2</SUB>-graphene heterostructure (MGH) on a 4 inch wafer at 300 °C by depositing a thin Mo film seed layer on graphene followed by sulfurization using H<SUB>2</SUB>S plasma. By utilizing Raman spectroscopy and high-resolution transmission electron microscopy, we have confirmed that 5–6 MoS<SUB>2</SUB> layers with a large density of sulfur vacancies are grown uniformly on the entire substrate. The chemical composition of MoS<SUB>2</SUB> on graphene was evaluated by X-ray photoelectron spectroscopy, which confirmed the atomic ratio of Mo to S to be 1:1.78, which is much lower than the stoichiometric value of 2 from standard MoS<SUB>2</SUB>. To exploit the properties of the nanocrystalline and defective MGH film obtained in our process, we have utilized it as a catalyst for hydrodesulfurization and as an electrocatalyst for the hydrogen evolution reaction. Compared to MoS<SUB>2</SUB> grown on an amorphous SiO<SUB>2</SUB> substrate, the MGH has smaller onset potential and Tafel slope, indicating its enhanced catalytic performance. Our practical growth approach can be applied to other two-dimensional crystals, which are potentially used in a wide range of applications such as electronic devices and catalysis.</P> <P><B>Highlight</B></P> <P> <UL> <LI> Practical growth for 2D MoS<SUB>2</SUB>-graphene heterostructure (MGH) was introduced. </LI> <LI> Low-temperature sulfurization of Mo thin film was realized by H<SUB>2</SUB>S plasma. </LI> <LI> As-grown MoS<SUB>2</SUB> film on graphene naturally contains large number of active sites. </LI> <LI> The MGH was shown enhanced electrocatalytic performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Electrochemical H₂O₂ biosensor composed of myoglobin on MoS₂ nanoparticle-graphene oxide hybrid structure

Yoon, Jinho,Lee, Taek,Bapurao G., Bharate,Jo, Jinhee,Oh, Byung-Keun,Choi, Jeong-Woo Elsevier 2017 Biosensors & bioelectronics Vol.93 No.-

<P><B>Abstract</B></P> <P>In this research, the electrochemical biosensor composed of myoglobin (Mb) on molybdenum disulfide nanoparticles (MoS<SUB>2</SUB> NP) encapsulated with graphene oxide (GO) was fabricated for the detection of hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>). Hybrid structure composed of MoS<SUB>2</SUB> NP and GO (GO@MoS<SUB>2</SUB>) was fabricated for the first time to enhance the electrochemical signal of the biosensor. As a sensing material, Mb was introduced to fabricate the biosensor for H<SUB>2</SUB>O<SUB>2</SUB> detection. Formation and immobilization of GO@MoS<SUB>2</SUB> was confirmed by transmission electron microscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, and scanning tunneling microscopy. Immobilization of Mb, and electrochemical property of biosensor were investigated by cyclic voltammetry and amperometric i-t measurements. Fabricated biosensor showed the electrochemical signal enhanced redox current as −1.86μA at an oxidation potential and 1.95μA at a reduction potential that were enhanced relative to those of electrode prepared without GO@MoS<SUB>2</SUB>. Also, this biosensor showed the reproducibility of electrochemical signal, and retained the property until 9 days from fabrication. Upon addition of H<SUB>2</SUB>O<SUB>2</SUB>, the biosensor showed enhanced amperometric response current with selectivity relative to that of the biosensor prepared without GO@MoS<SUB>2</SUB>. This novel hybrid material-based biosensor can suggest a milestone in the development of a highly sensitive detecting platform for biosensor fabrication with highly sensitive detection of target molecules other than H<SUB>2</SUB>O<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The electrochemical biosensor composed of the myoglobin on the graphene oxide (GO)-encapsulated molybdenum disulfide nanoparticles (MoS<SUB>2</SUB> NP) was developed for hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) detection. </LI> <LI> MoS<SUB>2</SUB> NP were encapsulated by GO (GO@MoS<SUB>2</SUB>) for the first time to induce the electrochemical signal enhancement. </LI> <LI> Fabricated electrochemical biosensor with GO@MoS<SUB>2</SUB> showed the stability and reproducibility. </LI> <LI> Fabricated electrochemical biosensor also showed the enhanced amperometric response current by detection of H<SUB>2</SUB>O<SUB>2</SUB>. </LI> </UL> </P>

Stacked graphene-MoS₂ photocatalyst for hydrogen evolution reaction

( Guo Wenwu ),김수영 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

The graphene and MoS₂ synthesized by chemical vapor deposition have been wildly studied and applied in many fields. Many researched about graphene- or MoS₂-based catalyst for hydrogen evolution reaction(HER) have been reported. In order to modify the electronic structure of graphene, doping method has been wildly investigated. It is reported that the graphene can be n-doped by stacking on MoS₂ because there is a work function difference between two materials. In this work, a graphene-MoS₂ photocatalyst was made by stacking graphene on MoS₂ and loaded on the p-Si electrode for water splitting to produce hydrogen. The performance of the stacked photocatalyst was checked by HER measurement and the respective quality of the graphene and MoS₂ will be discussed.

Exploring the correlation between MoS₂ nanosheets and 3D graphene-based nanostructures for reversible lithium storage

Son, Yoonkook,Lee, Jung-Soo,Choi, Min,Son, Yeonguk,Park, Noejung,Ko, Minseong,Jang, Ji-Hyun,Park, Minjoon Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.459 No.-

<P><B>Abstract</B></P> <P>Graphene-based materials are an attractive lithium storage material for next-generation lithium-based batteries due to its high capacity, surface area and conductivity. However, one of the major problems for its broad application in batteries is a large irreversible capacity, and the poor cycle stability and low rate capability remain. Here, we report a MoS<SUB>2</SUB>-stabilized hierarchical three-dimensional graphene-based nanostructure, in which the MoS<SUB>2</SUB> layer acts as a stabilizer as well as an active material. We show that the presence of MoS<SUB>2</SUB> thin layer adjacent to the graphene surface can improve lithium storage capability by improving lithium ion diffusion property with fast Li-ion transport kinetic. On the basis of experimental and theoretical approaches, we ascribe the improved reversible lithium storage to the unusual reversible Li-MoS<SUB>2</SUB> redox reaction and charge distribution on the graphene and MoS<SUB>2</SUB> interlayers. These findings will provide a potential new direction in the design of electrode materials for advanced lithium storage technologies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The development of MoS<SUB>2</SUB> nanosheet-assisted hierarchical 3D-graphene nanostructure. </LI> <LI> The study of mechanism for the improved Li ion transport capability on MoS<SUB>2</SUB> and graphene interlayer. </LI> <LI> The improvement of lithium-storage capability by Li ion diffusion with fast Li-ion transport kinetic. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>MoS<SUB>2</SUB> nanosheet-assisted hierarchical 3D graphene nanostructure was developed to improve Li adsorption property, in which MoS<SUB>2</SUB> layer went through the reversible Li redox reaction. We show that the presence of MoS<SUB>2</SUB> on 3D graphene surface can significantly improve lithium storage capability by improving Li ion diffusion property with fast Li-ion transport kinetic.</P> <P>[DISPLAY OMISSION]</P>

Large-Area Buckled MoS₂ Films on the Graphene Substrate

Kim, Seon Joon,Kim, Dae Woo,Lim, Joonwon,Cho, Soo-Yeon,Kim, Sang Ouk,Jung, Hee-Tae American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.21

<P>In this study, a novel buckled structure of edge oriented MoS2 films is fabricated for the first time by employing monolayer graphene as the substrate for MoS2 film growth. Compared to typical buckling methods, our technique has several advantages: (1) external forces such as heat and mechanical strain are not applied; (2) uniform and controllable buckling over a large area is possible; and (3) films are able to be transferred to a desired substrate. Dual MoS2 orientation was observed in the buckled film where horizontally aligned MoS2 layers of 7 nm thickness were present near the bottom graphene surface and vertically aligned layers dominated the film toward the outer surface, in which the alignment structure was uniform across the entire film. The catalytic ability of the buckled MoS2 films, measured by performing water splitting tests in acidic environments, shows a reduced onset potential of -0.2 V versus reversible hydrogen electrode (RHE) compared to -0.32 V versus RHE for pristine MoS2, indicating that the rough surface provided a higher catalytic activity. Our work presents a new method to generate a buckled MoS2 structure, which may be extended to the formation of buckled structures in various 2D materials for future applications.</P>

Rational design of multifunctional devices based on molybdenum disulfide and graphene hybrid nanostructures

Lim, Y.R.,Lee, Y.B.,Kim, S.K.,Kim, S.J.,Kim, Y.,Jeon, C.,Song, W.,Myung, S.,Lee, S.S.,An, K.S.,Lim, J. New York] ; North-Holland 2017 APPLIED SURFACE SCIENCE - Vol.392 No.-

We rationally designed a new type of hybrid materials, molybdenum disulfide (MoS<SUB>2</SUB>) synthesized by Mo pre-deposition followed by subsequent sulfurization process directly on thermal chemical vapor deposition (TCVD)-grown graphene, for applications in a multifunctional device. The synthesis of stoichiometric and uniform multilayer MoS<SUB>2</SUB> and high-crystalline monolayer graphene was evaluated by X-ray photoelectron spectroscopy and Raman spectroscopy. To examine the electrical transport and photoelectrical properties of MoS<SUB>2</SUB>-graphene hybrid films, field effect transistors (FETs) and visible-light photodetectors based on MoS<SUB>2</SUB>-graphene were both fabricated. As a result, the extracted mobility for MoS<SUB>2</SUB>-graphene hybrid FETs was two times higher than that of MoS<SUB>2</SUB> FETs. In addition, the MoS<SUB>2</SUB>-graphene photodetectors revealed a significant photocurrent with abrupt switching behavior under periodic illumination.

MoS2-Nanosheet/Graphene-Oxide Composite Hole Injection Layer in Organic Light-Emitting Diodes

박민준,NGUYEN PHAN THANG,최경순,박종이,Abdullah Ozturk,김수영 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.4

In this work, composite layers comprising two-dimensionalMoS2 and graphene oxide (GO) were employed as holeinjection layers (HILs) in organic light-emitting diodes(OLEDs). MoS2 was fabricated by the butyllithium (BuLi)intercalation method, while GO was synthesized by amodified Hummers method. The X-ray diffraction patternsshowed that the intensity of the MoS2 (002) peak at 14.15°decreased with increase in GO content; the GO (001) peakwas observed at 10.07°. In the C 1s synchrotron radiationphotoemission spectra, the contributions of the C-O, C=O, and O-C=O components increased with increase in GO content. These results indicated that GO was well mixed with MoS2. The lateral size of MoS2 spanned from a few hundreds ofnanometers to 1 μm, while the size of GO was between 400 nm and a few micrometers. Thus, the coverage of the MoS2-GOcomposite on the ITO surface improved as the GO content increased, owing to the large particle size of GO. Notably, GO withlarge size could fully cover the indium tin oxide film surface, thus, lowering the roughness. The highest maximum powerefficiency (PEmax) was exhibited by the OLED with MoS2-GO 6:4 composite HIL, indicating that similar contents of MoS2 andGO in MoS2-GO composites provide the best results. The OLED with GO HIL showed very high PEmax (4.94 lm W−1) becauseof very high surface coverage and high work function of GO. These results indicate that the MoS2-GO composites can be usedto fabricate HILs in OLEDs.